Styrene copolymers product distribution

Jackson and Walker [7] studied the applicability of pyrolysis combined with capillary column GC to the examination of phenyl polymers (e.g., styrene-isoprene copolymer) and phenyl ethers e.g., bis[w-(w-phenoxy phenoxy)phenyl]ether. In the procedure the polymer sample is dissolved in benzene. The pyrolysis Curie point temperature wire is dipped 6 mm into the polymer solution. The polymer-coated wires are then placed in a vacuum oven at 75-80 °C for 30 minutes to remove the solvent. Figure 6.2 shows a characteristic pyrogram of the copolymer (isoprene-styrene) resulting from a 10-second pyrolysis at 601 °C. When the polyisoprene is pyrolysed, C2, C3, C4, isoprene, and CjoHig dimers are produced. When PS is pyrolysed, styrene and aromatic hydrocarbons are the products. Figure 6.2 shows that the copolymer product distribution and relative area basis resemble the two individual polymer product distributions. 

A pyrogram of the copolymer (isoprene-styrene) resulting from a 10 s pyrolysis at 601°C yields product distributions similar to the sum of the two constituent product distributions. For example, when the polymer polyisoprene is pyrolyzed, C2, C3, C4, isoprene and Cjo dimers are produced. When polystyrene is pyrolyzed, styrene and aromatic hydrocarbons are the products. The copolymer product distribution and relative area basis resemble the two individual polymer product distributions. 

CO, COi, propene, isobutene, dimethyl ketene, acrolein, allyl alcohol, toluene, styrene, a-methylstyrene, ethylbenzene, glycidol, glycidylmethacrylate product distribution depends on copolymer composition... 

Trying to completely avoid the technically unpleasant process of chloromethylation, Negre et al. [48, 49] prepared a linear styrene copolymer with p-vinylbenzyl chloride and then subjected the product to self-crosslinking. Alternatively to the earlier-mentioned crosslinking of linear polystyrene with MCDE, this procedure results in local inhomogeneity of crosslinks distribution, because of the uneven distribution of the two comonomers along the initial chain (the monomer reactivity ratios of vinylbenzyl chloride and styrene are 1.41 and 0.71, respectively). Nevertheless, vinylbenzyl chloride became a popular comonomer for styrene and DVB in the preparation of beaded hypercrosslinked products [50-52]. 

Product distribution, variable or stepped pyrolysis and kinetic studies have all been used to expose mechanistic events during polymer degradation. For example, the thermal degradation of polystyrene has been elucidated using the block copolymer poly(styrene-b-styrene-dg). Hybrid and homo monomers (styrene) and dimers (2,4-diphenylbut-l-ene) were detected but without hybrid trimers (2,4,6-triphenylhex-l-ene) (Figure 10). The amount of hybrid dimer far exceeds that which might arise from adjacent residues, while similar proportions of dimers were obtained when the two homopolymers were pyrolyzed together. Data indicate intermolecular reaction rather than the previously proposed 1,3-transfer. 

Micromrxers in conjunction with serial microreactors can also be used effectively for LRP reactions, particularly for mixing viscous living polymer melts with non-viscous monomer for block copolymer production. For example, poly(n-butyl acrylate) can be synthesized in a microtube reactor via an N M P reaction, then the viscous homopolymer melt can be efficiently mixed with low-viscosity styrene monomer via a micromixer [90]. This can then be followed by N M P of the styrene on to the poly (w-butyl acrylate) chains in a second microtube reactor, thus creating a block copolymer. This technique gives a narrower molecular weight distribution product than comparable batch reactions. 

Similarly, the reaction of acetic acid with butadiene catalyzed by the same complexes is known to give, in homogeneous phase, a mixture of acetoxybutenes, acetoxyoctadienes, and 1,3,7-octatriene. This reaction has been effected with PdCh, Pd(PPH3)4, or Pd(OAc)2 anchored to diphenylphosphinated styrene—divinyl benzene copolymer [34g]. The product distribution is essentially the same as that... 

Jackson and Walker studied the applicability of pyrolysis combined with capillary column gas chromatography mass spectrometry to the examination of phenyl polymers (eg. styrene-isoprene copolymer) and polymer like phenyl ethers (eg. bis(m-(m-phenoxy phenoxy)phenyl)ether). They examined the effect of varying parameters affecting the nature of products formed and relative product distribution in routine pyrolysis. These parameters include the effects of pyrolysis temperature rise times, pyrolysis temperatures up to 985 C and pyrolysis duration. Temperature rise time (0.1 to 1.5 s) is not a critical factor in the Curie point pyrolysis of a styrene-isoprene copolymer, either with regard to the nature of the products formed or their relative distributions. Additionally, the variation of pyrolysis duration or hold time (2.0 to 12.5 s) at a fixed Curie temperature reflected no change in the nature of components formed however changes in product distributions were observed. Variations in Curie temperature at a fixed pyrolysis duration produced drastic changes in product distributions such as a three-... 

In styrene rich styrene/MMA (S/MMA) copolymers, the stability is intermediate between that of the two homopolymers, but the product distribution is strongly influenced by the presence of the MMA units. For example, in a 4/1 S/MMA copolymer, the yield of cold ring fraction products is about a third of that expected on the basis of the styrene content and the behaviour of PS, so that transfer reactions are considerably reduced. ... 

At 26.7 mbar pressure 40% weight toss main product is 2,4-diphenyl thiophene at least 11 unidentified minor products CO2, H2O, butene, isobutene, dimethyl ketene, styrene, methacrylic acid, succinic-type 5-membered cyclic anhydrides Chlorotrifluoroethylene, styrene, HQ, chloropentafluoropropene, ethene, chloroethene, totuene, a-melhylstyiene, dimer and trimer structures with some unsaturation S1F4 (fiom reaction of HF with glass). Distribution of products varies with polymer composition CO, CO2, propene, isobutene, dimethyl ketene, acrolein, allyl alcohol, toluene, styrene, cl-methylstyrene, ethylbenzene, glycidol, glycidylmethacrylate product distribution depends on copolymer composition... 

The most common VI improvers are methacrylate polymers and copolymers, acrylate polymers (see Acrylic ester polymers), olefin polymers and copolymers, and styrene—butadiene copolymers. The degree of VI improvement from these materials is a function of the molecular weight distribution of the polymer. VI improvers are used in engine oils, automatic transmission fluids, multipurpose tractor fluids, hydrautic fluids, and gear lubricants. Their use permits the formulation of products that provide satisfactory lubrication over a much wider temperature range than is possible using mineral oils alone. 

Such copolymers of oxygen have been prepared from styrene, a-methylstyrene, indene, ketenes, butadiene, isoprene, l,l-diphen5iethylene, methyl methacrjiate, methyl acrylate, acrylonitrile, and vinyl chloride (44,66,109). 1,3-Dienes, such as butadiene, yield randomly distributed 1,2- and 1,4-copolymers. Oxygen pressure and olefin stmcture are important factors in these reactions for example, other products, eg, carbonyl compounds, epoxides, etc, can form at low oxygen pressures. Polymers possessing dialkyl peroxide moieties in the polymer backbone have also been prepared by base-catalyzed condensations of di(hydroxy-/ f2 -alkyl) peroxides with dibasic acid chlorides or bis(chloroformates) (110). 

A combination of anionic and ATRP was employed for the synthesis of (PEO-b-PS) , n = 3, 4 star-block copolymers [148]. 2-Hydroxymethyl-l,3-propanediol was used as the initiator for the synthesis of the 3-arm PEO star. The hydroxyl functions were activated by diphenylmethyl potassium, DPMK in DMSO as the solvent. Only 20% of the stoichiometric quantity of DPMK was used to prevent a very fast polymerization of EO. Employing pentaerythritol as the multifunctional initiator a 4-arm PEO star was obtained. Well-defined products were provided in both cases. The hydroxyl end groups of the star polymers were activated with D PM K and reacted with an excess of 2-bromopropionylbro-mide at room temperature. Using these 2-bromopropionate-ended PEO stars in the presence of CuBr/bpy the ATRP of styrene was conducted in bulk at 100 °C, leading to the synthesis of the star-block copolymers with relatively narrow molecular weight distributions (Scheme 72). 

A second route is termed sequential anionic polymerization. More recently, also controlled radical techniques can be applied successfully for the sequential preparation of block copolymers but still with a less narrow molar mass distribution of the segments and the final product. In both cases, one starts with the polymerization of monomer A. After it is finished, monomer B is added and after this monomer is polymerized completely again monomer A is fed into the reaction mixture. This procedure is applied for the production of styrene/buta-diene/styrene and styrene/isoprene/styrene triblock copolymers on industrial scale. It can also be used for the preparation of multiblock copolymers. 

When butadiene and styrene are mixed in the presence of an organolithium initiator, the resulting copolymerization process and product will be governed by the reaction conditions. The rate of copolymerization, the relative composition of the copolymer, and the distribution of monomer units (i.e., block, random, etc.) will be determined by such factors as solvent, temperature, and monomer feed ratio. 

Polymers with even narrower mass distributions, e.g. with PDI values close to 1, arise in living polymerization systems, in which no chain termination processes can occur at all, such that all chains remain bound to the metal centre from which they have started to grow at the same time. Living polymerizations, which offer useful opportunities, e.g. with regard to the production of block copolymers by exchange of one monomer for another, occur in anionic polymerizations of styrenes or butadienes such as are induced by simple lithium alkyls. For a-olefin polymerization catalysts of the type discussed above, living polymerizations are rare. These more elaborate catalysts can thus release a newly formed polymer chain within a time interval of typically less than one... 

Other rubber systems have been commercially successful. Styrene block copolymers yield a HIPS product with a small particle size and provide high gloss. A mixed rubber system consisting of styrene-butadiene block rubber and/or ethylene-propylene diene modified (EPDM) rubber can be blended with the polybutadiene to form bimodal rubber particle size distribution for a... 

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